1. Field of the Invention
The present invention relates to the discovery of the human survival motor-neuron gene or SMN gene which is a chromosome 5-SMA (Spinal Muscular Atrophy) determining gene. The present invention further relates to the nucleotide sequence encoding the SMN gene and corresponding amino acid sequence, a vector containing the gene encoding the SMN protein or a DNA sequence corresponding to the gene and transformant strains containing the SMN gene or a DNA sequence corresponding to the gene.
More particularly, the present invention relates to means and methods for detecting motor neuron diseases having symptoms of muscular weakness with or without sensory changes such as amytrophic lateral sclerosis (ALS), spinal muscular atrophy (SMA), primary lateral sclerosis (PLS), arthrogryposis multiplex congenita (AMC), and the like. The methods for detecting such motor neuron diseases include, but are not limited to, the use of specific DNA primers in the PCR technique, the use of hybridization probes and the use of polyclonal and monoclonal antibodies.
Even more particularly, the present invention relates to the use of the human SMN gene or part of the gene, cDNA, oligonucleotide or the encoded protein or part thereof in therapy by insertion of the human SMN gene or part of the gene, cDNA, oligonucleotide or the encoded protein or part thereof, if required, into engineered viruses or vectors that serve as harmless carriers to transport the gene or part of the gene, cDNA, oligonucleotide or the encoded protein or part thereof to the body's cells including bone marrow cells.
The invention further relates to antigen sequences directed to the SMN gene.
In order to provide means for the therapy of motor neuron diseases, the invention also relates to the protein encoded by the SMN gene.
The present invention also relates to the isolation of the mouse SMN gene, the nucleotide sequence encoding the mouse SMN gene and corresponding amino acid sequence. A transgenic mouse model that hyperexpresses all or part of the SMN gene and a transgenic mouse model produced by homologous recombination with a mutated SMN gene is also described.
2. State of the Art
Degenerative motor neuron diseases can be placed into three major categories. Amyotrophic lateral sclerosis or ALS, motor neuron diseases such as spinal muscular atrophy (SMA) and motor neuron diseases associated with other degenerative disorders such as primary lateral sclerosis (PLS).
Amyotrophic lateral sclerosis (ALS) is the most frequently encountered form of progressive neuron disease and is characteristically a disorder of middle age. The disease is characterized by progressive loss of motor neurons, both in the cerebral cortex and in the anterior horns of the spinal cord, together with their homologues in some motor nuclei of the brainstem. It typically affects both upper and lower motor neurons, although variants may predominantly involve only particularly subsets of motor neurons, particularly early in the course of illness.
ALS is evidenced by the development of asymmetric weakness, with fatigue and cramping of affected muscles. The weakness is accompanied by visible wasting and atrophy of the muscles evolves and over time, more and more muscles become involved until the disorder takes on a symmetric distribution in all regions, including muscles of chewing, swallowing and movement of the face and tongue. Fifty percent of patients having ALS can be expected to die within three to five years from the onset of the disease. Presently, there is no treatment that has influence on the pathologic process of ALS.
Spinal muscular atrophies (SMA) are characterized by degeneration of anterior horn cells of the spinal cord leading to progressive symmetrical limb and trunk paralysis associated with muscular atrophy. SMA represents the second most common fatal, autosomal recessive disorder after cystic fibrosis (1 out 6000 newborns). Childhood SMA is classically subdivided into three clinical groups on the basis of age of onset and clinical course. The acute form of Werdnig-Hoffmann disease (Type I) is characterized by severe generalized muscle weakness and hypotonia at birth or in the 3 months following birth. Death, from respiratory failure, usually occurs within the first two years. This disease may be distinguished from the intermediate (Type II) and juvenile (Type III, Kugelberg-Welander disease) forms. Type II children were able to sit but unable to stand or walk unaided, and they live beyond 4 years. Type III patients had proximal muscle weakness, starting after the age of two. The underlying biochemical defect remains unknown. In addition there is known to exist a slowly evolving adult form of SMA, sometimes referred to as SMA IV.
Primary lateral slcerosis (PLS) is a variant of ALS and occurs as a sporadic disease of late life. Neuropathologically in PLS there is a degeneration of the corticospinal (pyramidal) tracts, which appear almost normal at brainstem levels but become increasingly atrophic as they descend through the spinal column. The lower limbs are affected earliest and most severely.
Arthrogryposis Multiplex Congenita (AMC) is a frequent syndrome characterized by congenital joint fixation (incidence of 1 out of 3000 live births) resulting from decreased fetal movements in utero (Stern, W. G., JAMA, 81:1507-1510 (1923); Hall, J. G., Clin. Orthop, 194:44-53 (1985)). AMC has been ascribed to either oligo-hydramnios or a variety of diseases involving the central nervous system, skeletal muscle, or spinal cord. Since neuronal degeneration and neuronophagia occur in the anterior horns, it has been hypothesized that the AMC of neurogenic origin could be related to acute spinal muscular atrophy; SMA Type I Werdnig-Hoffman disease (Banker, B. Q., Hum. Pathol., (1986); 117:656-672).
The detection and clinical diagnosis for ALS, AMC, SMA and PLS is quite limited to muscle biopsies, the clinical diagnosis by a physician and electromyography (EMG). For example, the clinical criteria for diagnosing SMA is set forth in the Clinical Criteria International SMA Consortium (Munsat T. L, Neuromuscular Disorders, Vol. 1, p. 81 (1991)). But due to the complications of the various tests to detect motor neuron disorders, the clinician usually attempts to eliminate various categories of other disease states such as structural lesions, infections, intoxications, metabolic disorders and hereditary biochemical disorders prior to utilizing the above-described test methods.
Presently there is no treatment for any of the above-mentioned motor neuron disorders. Basic rehabilitative measures, including mechanical aids of various kinds, may help patients that have these diseases overcome the effects of their disabilities, but often confining respiratory support systems are necessary to have the patient survive longer.
Accordingly, it is an object of the present invention to characterize the SMA gene which is responsible for SMA disorders and to clone the SMA gene into a vector, for example a plasmid, a cosmid, a phage, a YAC vector, that can be used in the transformation process to produce large quantities of the SMN gene and SMN protein.
In yet another aspect of the invention is the use of primers and hybridization probes to detect and diagnose patients having motor neuron disorders such as AMC, ALS, SMA and PLS. Yet another aspect of the present invention is the use of the SMN gene or part thereof or cDNA, oligonucleotides, protein or part thereof in therapy to correct disorders present in, for example AMC, SMA, ALS and PLS patients, especially gene disorders.
In yet another aspect, the present invention provides monoclonal and polyclonal antibodies for detection of SMN gene defects in SMA patients.
Another object of the present invention provides the characterization of the SMA gene in the mouse. A transgenic mouse model is presented that hyperexpresses all or part of the SMN gene or a transgenic mouse that by homologous recombination with a mutated mouse SMN gene produces abnormalities in the SMN gene is also described.
According to a further aspect of the invention, the therapy of motor neuron diseases can involve the protein encoded by the SMN gene.
These and other objects are achieved by the present invention as evidenced by the summary of the invention, the description of the preferred embodiments and the claims.